Fabrications Of Oxidized Starch/cellulose By Improved Fenton Reaction And Their Effects On The Properties Of Carboxylated Nitrile Butadiene Rubber/thermoplastic Starch

Starch and cellulose,as the most natural polymers,have the features of hydrophilicity and strong polarity with the polyhydroxyl in the glucose unit.In order to endow them with new properties,H₂O₂and low-concentration catalyst(Cu²⁺)were used to carboxylate the starch and cellulose in the controllable oxidation reaction.Then the oxidized starch(OST)and oxidized cellulose nanocrystal(OCNC)are added to the carboxylated nitrile butadiene rubber(XNBR)and thermoplastic starch(TPS)by chemical reaction and physical blending,respectively.The comprehensive properties of XNBR and TPS were significantly improved through the interface reaction,which provides a new method for the development and application of starch and cellulose.To fabricate antibacterial activity and simultaneous strengthened and toughened carboxylated nitrile butadiene rubber(XNBR)composites,starch was oxidized by H₂O₂ to achieve oxidized starch(OST)with different carboxyl content,meanwhile,ZnO were utilized to promote the in-situ interfacial reaction for improving compatibility of starch and XNBR.The formation of ionic cross-link networks and“Zinc-carboxylate polymers”in the XNBR/OST/ZnO composites were confirmed by FT-IR,XRD,XPS,SEM-EDS and TEM.Interestingly,because of the carboxyl groups of OSTs which provided a low p H surroundings to inhibit the growth of bacteria,XNBR/OST/ZnO composites achieved a significant antibacterial activity.Noteworthy,the sulfur-free XNBR composites achieved 3.1 and 1.9 times increase for tensile strength and elongation at break compared with neat XNBR.The mechanism of simultaneous strengthened and toughened for composites had been proposed.These new sustainable,green and facile fabricated XNBR/OST/ZnO could be utilized as the medical protective appliance to against the bacteria.Targeted modification and efficient utilization of existing bio-based reinforcing fillers are of great significance for the development of the rubber industry.In this study,the oxidized cellulose nanocrystal(OCNC)was served as anchorage sites of Zn²⁺-carboxylate bonds and curing agent precursor,and the XNBR/OCNC/ZnO cross-linked composites were prepared by in-situ interfacial reaction with XNBR under two-roll open mill.The microstructure and morphology of the composites were characterized,and the effects of OCNC and ZnO on the performance of the composites were also investigated.With the transmission of Zn²⁺-carboxylate cross-linked network,OCNC endows the composites with excellent wear resistance(90%decrease in relative mass loss and 35%increase in hardness compared to neat XNBR),irradiation aging resistance,and antibacterial properties.In addition,the tensile strength and elongation at break of the sulfur-free composites were substantially improved compare with neat XNBR.The enhancement of the composite is attributed to the generation of multiple cross-linking sites(i.e.,OCNC-ZnO integrator)through the reaction of ZnO and OCNC with abundant carboxyl groups,and then the formed OCNC-ZnO integrator can be further reacted with XNBR to obtain enhanced Zn²⁺-carboxylate cross-linking network through in-situ interfacial neutralization reaction.This study provides a universal,simple and scalable method for the fabrication of multifunctional rubber composites by constructing Zn²⁺-carboxylate cross-linked network with natural cellulose resource.Sustainability and biodegradability have attracted interest in thermoplastic starch(TPS)based bionanocomposites.Herein,microcrystalline cellulose(MCC)was oxidized by H₂O₂/Cu SO₄,a new Fenton process,to achieve oxidized cellulose nanocrystals(OCNCs)with17.1%carboxyl content.The structure and morphology of OCNCs were carefully characterized by titration,intrinsic viscosity,XRD,FTIR,¹³C-NMR,SEM and TEM,respectively.Noteworthy,the thermal stability of the OCNCs was superior to CNCs prepared by acid hydrolysis via isothermal thermogravimetric analysis.Interestingly,selective oxidation for the primary alcohol groups of MCC was occurred and the OCNCs achieved the average diameter and length,degree of crystallinity which were 11.0 nm,231.6 nm and 72%,respectively.Then glycerol,starch and OCNCs were reactive extruded by twin-extruder to prepare TPS/OCNC bionanocomposites and their structure and performances were evaluated by dynamic DMA,TGA,FTIR,XRD,SEM,tensile and impact testing.Strikingly,significant improvement in glass transition temperature(from 63.1°C to 94.5°C)and notch impact strength(from 1.3 to 3.9KJ/m²)were noted for the amorphous TPS/OCNC bionanocomposites with an OCNC content of only 1 wt%,and its tensile strength achieved 20.5 MPa,simultaneously.The improved mechanism of these performances was assigned to In-Situ forming“Carboxyl-Hydroxyl”hydrogen bonds which acted as the physically cross-linking interactions and improved the interfacial compatibility.We hence showcase Fenton reaction and reactive extrusion here as the facile strategy to prepare sustainable and biodegradable TPS/OCNC bionanocomposites with properties more suitable for daily applications to replace petroleum-based plastic materials and eliminated the pollution of“microplastics.”...